POWER October 2011 - 26

The best explanation for this condition was that water residues
10. Easy inspection. When inspecting a condenser with a header
box, an extension tube is fitted to the APR probe to span the box, and
the inspection is then carried out as usual. Source: AcousticEye
had been left in the tubes when the condenser was put into service.
The source of these residues was assumed to be the hydrotesting that
had been carried out upon installation, three years earlier.
At this point the operator was left with two possibilities: the
very expensive prospect of replacing the problematic condensers
or cleaning out the corrosion. The operator's main concern was
that, after cleaning, the tubes would be shown to be in such
bad condition that they would have to be replaced anyway. The
decision was made to first clean out a single condenser unit and
inspect the tubes.
The leaking condenser was hydroblasted and then inspected
by a commercial service provider, using APR. Several additional
holes were found, as were tubes with severe pitting. However,
the majority of tubes were in satisfactory condition.
In view of the condition of the tubes after cleaning, and the
rapid inspection time available with APR, the operator made two
major decisions:
■ To follow the initial approach of cleaning out the entire bank,
then inspecting all the tubes with APR, and plugging the problematic
ones. A full inspection over a short outage would not
be possible with other technologies.
11. A hole pattern. An APR inspection returns electronic signatures
that represent faults. Different discontinuities have different signatures.
In this figure, a leaking hole is observed. Source: AcousticEye
x10ˆ-4 Position: 17.33307165 Value: -0.00000918
4.5
3.6
2.7
1.8
0.9
0.0
-0.9
-1.8
-2.7
-3.6
-4.5
-5.4
15.2 15.4 15.6 15.8 16.0 16.2 16.4 16.6 16.8 17.0
Mean: -0.00000 Min: -0.00079 Max:-0.00068
 5%
■ To purchase the APR equipment, train several of the company's
own people, and carry out the inspection itself. This was made
possible through the high level of automated analysis available
in this equipment, which enables technicians to use it
properly after a training course of only two days.
The entire bank was hydroblasted and treated with a chemical
wash intended to coat the tubes to prevent further corrosion.
The remaining 2,840 tubes in the unit (10 condensers with


m_142
284 tubes each) were inspected in two days. In contrast to many
condenser types where removal of access plates makes tube ends
available to direct inspection, these condensers have a header
box, about 12 inches deep, at either end. Opposite each tube is
a plug that can be removed to enable inspection. Nevertheless,
inserting an eddy current probe across the gap between the plug
hole and the tube is awkward and time-consuming. Using APR,
an extension tube is fitted to the APR probe, and the inspection
is then carried out as usual (Figure 10).
A detailed report was provided in two additional days, recom17.2
17.4
mending that about 4% of the tubes be plugged. When the unit was
brought back online, losses of organic gas dropped back down to normal
background levels and overall plant output increased by 1.5%.
12. Fault report. A complete picture of the condenser material
condition can be reported on a single figure based on the individual
reports (see Figure 11). Source: AcousticEye
● No fault, or erosion <10% of tubewall depth
● Wall depth erosion / pitting >70%
● Full blockage
● Wall depth erosion/pitting 10%-30%
● Many/massive partial blockages
● Wall depth erosion/pitting 30%-70%
● Holes
26
Useful Report Extracts
Many interesting and useful observations were made, based on the
measurements. For example, the signals in Figures 6 and 7 were
taken from one of the inspected condensers. Numerous positivenegative
peak patterns can be seen, indicating the presence of
many blockages. Most of these were quite small, having some effect
on the efficiency of the unit, but not justifying a complete
replacement. Figure 11, on the other hand, shows a typical signature
of a hole. A final report was then prepared for each condenser,
reporting all faults in graphic and tabular form (Figure 12).
APR has been demonstrated in the field as a viable tool for
condenser tube inspection. Both test time and report generation
are fast in comparison to existing nondestructive inspection
technologies. APR enables 100% inspection of large condenser
banks while maintaining very short downtimes. ■
-Contributed by Dr. Noam Amir (noam@acousticeye.com), chief
technology officer, AcousticEye.
www.powermag.com
POWER | October 2011
http://www.powermag.com
POWER October 2011

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